CLIMATE change is likely to increase landslides, but it isn’t thing that will increase landslides the most.

The culprit, the biggest driver of landslide events, is a more basic, says Professor Dr David Petley.

It’s the growth of cities.

While scientists and governments puzzle over how climate change will impact rainfall and the number of landslide events in a year, this engineering geologist from the International Landslide Centre at Durham University warns about serious and more easily visible problems.

“Climate change is terribly important and we have to find ways of reducing carbon dioxide emissions quickly or we will face a very dire situation.
“But that’s not the only crisis we are facing.

“What’s likely to increase landslides the most, are cities moving out into more and more marginal land.

“If this is poorly planned or poorly constructed housing development, it poses a real threat in terms of landslides,” said Petley who delivered keynote address on the subject at the International Conference on Slopes 2008.

Petley said this is evident to some extent in Kuala Lumpur and that’s why the proposed National Slope Masterplan is so important.

“As KL expands and slopes are developed, having a policy and body that makes sure that development is done properly is critically important.”

The second key factor, said Petley, is deforestation. Though not as great a concern in Malaysia as in other Asian countries, the country is still likely to be impacted by the conversion of forests into other uses.

“There will be more pressure to turn land into palm oil plantations in order to generate oil and that can lead to degradation of the environment.

“We’ve seen in many places that deforestation and conversion to plantation are environmentally very serious.”

Petley also linked the issue of deforestation to what he termed Asia’s “next great threat”: population growth.

As population density goes up, each fatal landslide incident is likely to claim more lives, he explained.

The United Nations Habitats Programme projects that between 2000 and 2030, the population of Asia would increase by about 1.2 billion people, the most in South Asia, which is expected to gain 700 million inhabitants.

Over the same period Asia’s urban population is expected to increase by 1.3 billion.

A substantial proportion is expected to come in the form of urban slums that will inevitably result in the occupation of some land with marginal stability.

“The population we now have is living in most of the land that’s suitable to live in, so as the population grows we are inevitably going to push into more and more difficult areas.

“Those people will need to be fed, so more land will be transferred to produce food, and this could lead to more landslides.”

Petley illustrated his point using the example of Haiti and the Dominican Republic, two countries that share an island.

Haiti has very high population growth and a very poor population. Here the mountainsides have almost completely been deforested and most marginal areas have been inhabited.

“If you do take a look at the two countries on Google Earth, you can see the line – one side deforested and the other forested, because the Dominican Republic has been much better at preserving their forests.

“Haiti has had just the most terrible series of landslide disasters – 600 people killed this summer in landslides disasters. The Dominican Republic doesn’t have this problem.”

So while climate change should be taken seriously, the focus shouldn’t be taken off other environmental stresses that play a more significant role in dramatically increasing the number of landslide tragedies.

The trick, he said, was to find a balance between the short term problems and the changes we expect to see in the next 50 or more years.

Pinpointing the very short term needs such as locations in need of immediate repair and implementing measures to reduce landslide risk quickly would be sensible.

It would also be crucial to look study what the combination of climate change, population growth and urban development would do, and modify some of those short term plans with the future in mind.

And all these threats and changes, do not spell the end to all hillside development, said Petley.

It is possible to develop hillsides safely but it does require investment to do it.

He cites the example of Europe that has seen many landslides and has much landslide-prone terrain.

Despite this, few lives are lost because Europe’s population, authorities and engineers have become very good at dealing with it, said Petley.

The most dangerous landslides are nearly always mitigated and where they aren’t, they are identified and people are relocated.

In a developing economy like Malaysia, where hillside locations are expensive and attractive there is in fact hope, he said.

Hope because it provides an opportunity for higher enforcement of regulations.

“You can have a series of guidelines that force people to develop their hillsides properly to high standards of design.

“Whereas if you go to Philippines, the hillside is occupied almost entirely by the poor and development is totally unplanned.

“As long as you have a set of strong guidelines, enforcement and an agency to monitor, it can be controlled.”

Petley believes that of all natural disasters, slopes-related disasters are the most manageable.

When compared with volcanoes and earthquakes, the one that were the best at dealing with is landslides.

We can identify areas that likely to suffer landslides, create warning systems in large areas or on specific slopes and stabilise slopes.

But there are certain prerequisites for success: a proactive approach to managing slopes, strong government will and a series of measures to ensure that management happens.

This, said Petley, included people trained appropriately to manage slopes, a set of standards for building design.

It also meant having an agency to design and implement warning systems, to coordinate research and one given the authority to implement the plans.

“There is a real danger everywhere that because of the combined pressure of changing climate, development and pressures on land, the toll from landslides will rise through time.

“It will rise quite quickly and that’s what we’ve seem in other countries. So proactive government intervention here, to start to bring the risk down, is a good move.

“But it now needs implementation.”